Non-absorbable silicone coated sutures and method of making



June 8, 1965 A. GLICK 3,187,752

NON-ABSORBABLE SILICONE COATED SUTURES AND METHOD OF MAKING Filed April27, 1962 j z INVEI qTOR.

ARTHUR GL ICK BY M Wmm United States Patent 0 3,187,752 NUN-ABSORBABLESILICGNE COATED SUTURES AND METHGD 0F MAKDIG Arthur Gliclr, Danbury,Count, assignor to American 1(Iqyanamid Company, Stamford, Conn., acorporation of ame Filed Apr. 27, 1962, Ser. No. 199,604 26 Claims. (Cl.128--335.5)

This application is a continuation-in-part of application Serial Number767,502, filed October 16, 1958 and now abandoned.

This invention relates to a non-absorbable densely constructed suturebuilt up of a plurality of filaments 113V, ing a serum-proof,moisture-resistant coating on the surface of the individual filaments,which coating contains a silicone resin.

As used in this specification the term suture is intended to includeboth sutures, as are used for the sewing of tissues, and ligatures asused for tying off blood vessels, etc. Different portions of one strandmay be used for both purposes in the same operation depending upon theneeds of the surgeon at the particular moment.

In surgical practice; and for present purposes, this includes both humanand animal surgery, two classes of sutures are commonly used. One is theabsorbable suture which is absorbed by the tissues and accordingly losesits identity, such sutures usually being of catgut, etc.; and the otherform is a non-absorbable suture which in most instances is permitted toremain as such pen strong and should maintain their strength andintegrity for prolonged periods while in contact with body tissues andfluids. It is desirable that such sutures be inert, causing a minimum oftissue irritation, and that the diffusion of fluids through the sutureby capillarity be at a minimum. 1

It has been customary to use silk sutures built up as by braiding,Weaving, twisting or spinning, hereafter called coordinateconfiguration, of from a plurality of individual silk filaments.Synthetic polymers may be used instead of natural silk. These filamentspresent a construction in which there are fine interstices which bycapillary action cause fluids to travel along the length of the suture.This may permit migration of pathogenic organisms.

Accordingly, such sutures have been coated with waxes, such as beeswax,or beeswax mixed with ethyl cellulose, which material reduces thecapillarity of the suture and improves the handling characteristics ofthe suture.

There is some evidence that under some conditions these waxes causegranuloma formation, and have other undesirable side ellects.

Additionally the coating material should be inert to all body fluids andheat stable to permit heat sterilization of the suture. It is desirablethat the coating be economical and readily applied.

In addition to the physiological properties of inertness thecharacteristics of handling and of strength of a suture are extremelyimportant. It is desirable that a suture be sufiiciently still that itcan be easily handled and yet readily formable to a new position. Afterbeing bent to a new position, it should maintain this new set position.Many fibrous materials have a plastic memory, and after being bent to anew position slowly on standing tend to go back to their former shape. Asuture should not have plastic memory but should when once set maintainthat new position.

Additionally the suture should be easy to tie in a knot and should beresistant to knot-slippage under strain and the knot should remainsecure and not slip or untie itself on standing. Additionally, a sutureshould have what is known as throwability. That is, the surgeon shouldbe able to pick up the suture and throw it to a new position, whichposition is then retained. It is desirable at' times to place a suturein a given location or throw it in a given direction with the knowledgethat the suture will stay there until-positively moved.

In the past a great deal of the handling characteristics have beenimparted to a limp suture by the coating material. Beeswax or beeswaxmixed with ethyl cellulose used as a coating is responsible for thedesirable handling characteristics.

If some other coating material is used with the same filamentconstruction, the sutures may not have satisfactory handlingcharacteristics.

it has now been found that by braiding a suture with a tighter and moredense construction using fewer picks, i.e. cross-overs per inch, and bydry stretching the braided filaments, a suture can be formed which hasinherently stiffer qualities and improved handleability.

Silk is the usual material used for non-absorbable sutures. Syntheticfilaments such as nylon, polypropylene, Or-lon, polyacrylonitrile,Dacron, a stretched oriented polyester of ethylene glycol andterephthalic acid, etc., or cotton, or linen are sometimes used.Occasionally such materials as stainless steel or horsehair are used.All such materials can be advantageously coated with polymericsilicones, in accordance with this invention, and are braided or spun orformed more tightly for coating with silicones than with conventionalcoating materials.

Polymeric silicones are applied to this denser suture; such polymericsilicones readily coat the individual filaments increasing theresistance to aqueous fluids thus a reducing capillarity. Furthermore,such silicones applied'as a coating are heat stable. In at least someinstances the coating may be applied in a partially polymerized stateand the silicone further polymerized in position on the suture.Fortunately and fortuitously, polymerization catalysts are decomposed byheat sterilization procedures or heat curing so that even if toxiccatalysts are used as a component of the silicone coating, the finalproduct is completely inert.

The particular silicone resins themselves are not a part of thisinvention and standard commercial resins may be used. It is notnecessary that the material be applied as a liquid, as some of thesesilicone resin forming materials, such as the General ElectricDrifilrns, are volatile and may be applied in the gaseousphase. Thesematerials are among the volatile silicone compounds such as alkylsilicone halides. A material such as dimethyl silicone dichloride iscomparatively volatile and may be applied either direct or by allowingan ethereal solution thereof to evaporate and the vapors contact thesuture material.

Frequently, it is more convenient to use a liquid preparation. Suchpreparations are solvent dispersions of silicone resins, that ispartially olymerized products which will polymerize to a silicone film.For purposes of convenience it is normally easier to purchase thematerial under trade-names rather than making it, or obtain it to aperformance specification. Materials which are sold commercially such asthe Dow-Corning silicone DC DC 804 or General Electrics 9980 give highlysatisfactory and useful films. To those skilled in the art of siliconecompounding it is comparatively simple to select a heat-curable orpotentially heat-curable silicone resin, which either from itsinherentcharacteristics, or

s eaves :3 the addition of a polymerizing catalyst, will set up or cure.As a final check to insure the complete removal oi all halide tosilicone linkages, ammonia fumes may be used. Usually sufiicientmoisture is present to insure the hydrolysis of the halogen, but ammoniafumes insure a neutral product. I desired, silicone containing resinsmay be used in which the silicone atoms are linked through nitrogen,from ammonia, rather than through oxygen as in the silicones, suchresins at times being referred to as silamines.

Methods for preparation of silicone resins are well known. Patent No.2,306,222 to W. I. Patnode, Method of Rendering Materials WaterRepellant, discloses the use of a vapor of an alkyl silicone halide formaking glass vapor-proof. The same types of materials as thereindescribed may be used to water-proof and treat sutures. The patent toSafford, No. 2,424,853, and the patent to Tanis, No. 2,408,822,additionally describe siliceous halides and their conversion to resins.There are several methods of preparing such silicone resins, amongothers are the reaction of Grignard type reagents with a siliconetetrahalide. From the standpoint of costs silicone tetrachloride isnormally used and the Grignard may be either alkyl or aryl or a mixturethereof. The amounts of alkyl and aryl groups used affect thebrittleness and rate of cure of the resin formed. Normally the productof the reaction of the Grignard reagent with silicone tetrachloride isallowed to react with moisture, allowed to partially polymerize, and thepartially polymerized materials are dissolved in a suitable solventwhereby additional polymerization is either inhibi ed or substantiallyslowed down; The higher the ratio of lower alkyls, the more rapid thematerials will cure and the more brittle will be the film. The morehighly branched the chains formed in the resin, which are necessarilyformed by the polymerization of the silicone types containing morehalide atoms per silicone molecule, the more brittle and polymerized arethe resins.

The organo-silicones sometimes referred to as organopolysiloxanes, moreparticularly the hydrocarbon substituted polysiloxanes are particularlysuitable for suture coating. The patent to Wright et al., No. 2,389,477,entitled Polysiloxane Resins gives considerable information'or" thistype of resin. Certain of the resins which are described in the patentto Hyde, No. 2,386,466, Insulated Conductor and Insulation Therefor, itdiluted with body fluids. in neural surgery, suture materials frequentlydeleteriouslyaifect regeneration of nerve fibers. Silicone coated silkis the first material known to have been successfully used in suturingnerve fibers which permits the regeneration of the nerves in the spinalcolumn.

Usually silk is braided loose enough for a beeswax coating to impregnatethe silk, reduce capillarity, and impart desirable handling qualities.The new silicone coating may not inherently have enough body to give thedesired handling qualities. Rather than use a more highly polymrized'silicone resin, which is stiller, it is preferred to use a denser silkconstruction, with more silk filaments in a given cross-section. Thisgives a greater strength, and a thinner silicone coating gives a properinertness to the suture and at the same time prevents capillarity.

One standard test for capillarity is to boil two 3 to 4 inch lengths ofthe suture in distilled water in a glass container for three successive20-minute periods, changing the water each time. After the thirdboiling, the test sutures are allowed to stand for at least 8 hours inan atmosphere having a relative humidity of 65% 12% at a temperature of2lil C. The segment of suture is tied to a piece of white silk threadwith a square knot, the ends cut close, and suspended by the white silkthread so that the suture dips into a 0.5% aqueous solution of methyleneblue, with the knot %-inch above the dye solution. After standing for 24hours, the white silk is inspected for evidence of dye carried up thesuture by capillary action. It the white silk is free from dye color,the suture is non-capillary, and passes the test. Both of the duplicatesamples should pass.

Sutures of this invention pass this test for capillarity. Sutures whichpass this test'are non-capillary in tissues of man and animals.

For preventing slippage at knots in the suture, a coating formingahardened, but flexible silicone film ispreferred, using a siliconehaving a higher ratio of with a solvent may be used in accordance withthe instant invention. The patent to Hyde, No. 2,371,050, Organo-Silicone Polymers and Method of Making Them, de-

scribes certain additional methods of preparing such resins. It is notnecessary that the resins be prepared from halogen containing compoundsas, for example, methods such as set forth by Strain et al. in PatentNo. 2,394,642, Silicic Acid Esters, describes a difierent form ofsilicone containing resin. The patent to Iler, No. 2,395,550, ModifiedAlkyd Resins, describes still further modifications of siliconecontaining resins in which the silicone linkages are different thanthose classified as organo-polysiloxanes.

It is not intended that a treatise be here included on the production ofsuch resins, as such resins are the invention of others and areadequately described in the patent literature, as well aselsewhere. Thetexts Introduction to the Chemistry of the Silicones, Eugene G.

,closes some of the silicones which may be used, and other medicalusages for such silicones.

The silicone acts as a protectivc'layer on the surface of the filaments,and prevents dyes or the surface characteristics of the filaments,suchas silk, from interacting aryl groups. For instance, a polysiloxanehaving from about 72% to 67% methyl substituents and from 28% to 33%phenyl groups cures to a non-slipping finish that gives excellent knotretention. Usually the suture breaks before the knot slips. Also suchpolysiloxanes are sufficiently adhesive that spun sutures of silk orother filaments do not unravel, or broom, and can bethreaded intoneedles. 7

The silk construction itself rather than the coating can beused to givethe handling qualities.

Whereas the number of ends, and total denier, varies with size, it isdesirable that a maximum size, and

strength be obtained within the overall limits of suture diameter. Forthe standard United States Pharmacopeia sizes (United StatesPharmacopeia Convention, Inc., Distributed by Mack Publishing Co.,Easton, Penn., elsewhere abbreviated U.S.P.) this is:

U.S.P. Picks per Denier U.S.P. size diameter, inch of raw inches, max.silk used The picks per inch are the number of threads, running in onedirection, per lineal inch of suture.

The silk is braided using a smaller number of picks than conventional,and with a larger core size. The braided'silk is washedto degurn, thendyed, if desired, in skeins in accordance with conventional practice.The silk is dried, and then dry stretched from. about 6% to about 11% ofits length. This stretching tightens the braid, and gives a more dense,more handleable silk. At least some of the stretching may beaccomplished while the silk is wet.

The raw silk used has a total of about 378 denier.

white felt.

After stretching the silk suture ,is passed through a solvent bathcontaining the polymeric silicone. Such solvents as xylene, toluene,benzene, gasoline, or other non-toxic volatile hydrocarbon solvents maybe used. In addition to the silicone, beeswax, ethyl cellulose or a lowmolecular weight polyethylene may be dissolved and used as part of thecoating. For the silicone rubbers, a catalyst is usually used toaccelerate the curing rate. The standard organic peroxides, of whichbenzoyl peroxide is the most frequently used, are suitable catalysts, 2%to by weight of the polymer gives good results. The heat which sets theresin decomposes residual peroxides to give non-toxic products. For thehardened, flexible films, having a higher percentage of phenyl groups,heat alone can cure the silicone. Organo metallic driers such as zincoctoate, or iron stearate accelerates the cure. Nontoxic salts of metalswith fatty acids are effective.

A 2% to 50% solids bath gives a satisfactory coating.

A 5% to solids concentration in the bath results in easier operatingcontrol. A 20% concentration is usually preferred. While an adequatepick up with a single coating bath is obtainable, more uniformdistribution and coating can be obtained by using two or more baths,with heat curing between coatings. A cure temperature of at least 150 C.for 30 seconds gives a cure, al-

though longer times at lower temperatures, or a longer cure with lesscatalysts, etc. in accordance with standard practice in the silicone artmay be used.

A total weight of coat of 2% to 20% by Weight of the fiber gives goodcharacteristics. This percentage is called the pick up.

The sutures are shown in the attached drawings:

FIGURE 1 is a cross-section of a silicone coated suture.

FIGURE 2 shows a portion of an eight carrier on a 16 capacity carrierbraider formed braid.

FIGURE 3 shows a portion of a sixteen carrier braid.

EXAMPLE 1 A silk suture is braided, using 8 carriers,'on a sixteencarrier braider, with 3 ends of 13 to 15 denier silk per carrier, and acore of 3 ends of 13 to 15 denier silk, and picks per inch, giving theskipped braid of FIGURE 2. (The denier is the weight in grams of 9000meters of the strand.) The braided suture is washed to degum, thendried, while looped in skeins. The dry silk is stretched 9% of itslength, which gives improved stifiness; and increases the density.

A silicone rubber sold as Silastic 9711 by Dow- Corning is milled intosheets of about /s-inch thick, and thereto while milling additionally isadded 8.46% by weight of the rubberof a silicone fluid containing byweight benzoyl peroxide (Luperco ASF). After milling for an additional 5minutes, the sheets are cut into small pieces and soaked overnight inxylene. The swollen silicone is stirred to a cream-like consistency,then diluted to 20% solids, and stirred until uniform.

The braided silk is immersed in a trough of the silicone solution atroom temperature, then wiped over a piece of The coated silk is passedthrough a three stage heating tunnel, so that the silk is heated for oneminute each at 100 C., 125 C., and 150 C. The silk is spooled after aircooling.

This coating procedure is repeated. In the double c'oa'ting, the'silk isfound to have picked up 15% by weight of the silicone coating.

The finished suture gauges 0.0077 inch in diameter and is a 4-0 suture.

A conventional braiding of a 4-0 suture gives about 60 to 70 picks perinch, and uses 8 carriers with 2 ends of 20-22 denier each, and nocore.- Such a silk suture has a total denier of about 336, and if coatedwith bees wax in accordance with conventional practice gauges .0083inch.

length as to heat the silk suture for two minutes.

Other characteristics for comparison are:

Silk Silk With With New Old Silicone Beeswax Picks per i nch 40 60Gauge:

Raw int-he 0076 0081 sterilized d0 0077 0083 Straight pull sterilizedpounds 3. 17 2. 68 Knot pull sterilized do 2. 04 1.80 Pliaoility tobend, raw mgs 117 102 Stifinessinches self support Horizontal (sterile)inches 2. 94 4. 75 Vertical (sterile) do 4. 00 5.13 Apparent density asbraided gms./cc- 1.127 0.927

The increase in strength after sterilization both straight and over aknot shows the new silicone construction to have marked advantages. 7

The suture is sterilized either by conventional autoclaving procedures,or by ethylene oxide gas, in accordance with commercial practice in theindustry.

The individual silk filaments of the braid are shown at 10, thefilaments of the core are shown at 11, and the suture has a siliconecoating 12. FIGURE 2 shows the construction of a 000 suture, otherwisethe same as above.

EXAMPLE 2 The coating of the suture of Example 1 is repeated using a 15%solids solution of a dimethy silicone polymer of the general formula (CHSiO) with 5% by weight of the polymer of benzoyl peroxide as catalyst.After two coatings, a readily handleable suture is obtained.

EXAMPLE 3 A multi-filament 4-0 sized silk suture braided as in Example 1is washed and dyed black in accordance with conventional procedures. Thesuture is then dry stretched. An alkyl polysiloxane sold by GeneralElectric as Drifilm 88 is diluted with toluene to form a 10% siliconesolids solution. The silk suture is immersed in the toluene solution ofthe silicone resin at 50 C., then drawn through a curing tunnel at atemperature of C., and of such The suture may be heated longer, so as tosterilize thesuture at this time after which it is sterilely packed andhandled until used by the surgeon; or after the two-minute heating, thesuture may be reeled and packaged using clean but not sterile techniquesand finally sterilized by dry heat after packaging and prior to sale, orjust prior to use by the surgeon.

EXAMPLE 4 the coated silk is heated to 130 C. for three minutes. i

The silk suture may be sterilized by heating, as desired, but beforeuse. About 12% by weight of the silk of the silicone remains in thecoating.

EXAMPLE 5 The silicone rubber sold as Dow-Corning Silastic 9711 ismilled with 4.2% of benzoyl peroxide for five minutes, out into smallpieces, covered with xylene, and soaked overnight. The swollen materialis stirred with additional xylene to obtain a 20% solids concentration.

Braided silk prepared as described in Example 1 is passed through thesilicone in xylene, wiped with a piece of white felt, then cured for oneminute each at temperatures of 100 C., 125 C., and 150 C. The silk picksup about A multi-filament size 3-0 braided polyester suturewas .coatedin two passes with a silicone rubber bath containing 17% silicone solidsdispersed in xylene. The coating and curing procedure was as describedin Example 5. The suture picked up 2.9% by weight of silicone solids.The polyester suture iwas non-capillary.

EXAMPLE 7 A multi-filament 241 silk suture was braided using 16 carrierseach containing 3 end denier silk; a core of 14 ends 20-22 denier silk;a pick count of and a total denier of 966. The construction is of thetype shown in FIGURE 3. The braided suture was coated with a methylphenyl polysiloxane which contains about 72% methyl groups and 28%phenyl groups. The coating bath con tained 35% silicone solids in xylol.The excess coating was wiped off with apiece of sponge rubber and thecoating was cured for one minute each at temperatures of 100-C., 125 C.,and 150 C. The silk picked up 7% by weight of silicone solids for onecoat. A second coat under the same conditions yielded a total pick up of12%. The silk at both coating levels Wasnon-capillary, had good bond andshowed good resistance to brooming. Surgeons knots tied in the silkbroke before slipping.

EXAMPLE 8 A multi-filament spun, or twisted, 3-0 silk suture was coatedwith a methyl-phenyl polysiloxane, processed and cured as in Example 7.The spun and twisted silk had a silicone pick up that ranged from 7% fora single coat to 12% for a double coat. The silk did not broom or bushand the filaments were bonded together, so that a needle could bereadily threaded.

EXAMPLE 9 A multi-filament size 3-0 braided nylon suture was coated intwo passes in a silicone rubber bath containing 17% silicone solidsdispersed in xylene. and curing procedure was that described in Example5. The nylon suture picked up 4.5% by weight of silicone solids and wasnon-capillary. Good results were obtained when used in surgery.

EXAMPLE 10 A multi-filament braided 3-0 suture was coated with a bathcontaining 30% solids of a silicone resin commercially sold asDow-Corning 804. This resin is a comparatively short chain siliconeresin containing both phenyl and methyl substitutents on the siliconeatoms. Added to this bath was a plasticizer amounting to 20% of theweight of the silicone solids. The silk was immersed in this bath, theexcess silicone wiped off with sponge rubber and the silicone was curedin a tunnel for one minute each at temperatures of 100 C., 125 C., and150 C. The silk for a single coat had a silicone pick up of 7% of theweight of the silk. Silk with two coats had a pick up of 12% siliconeresin- Silk coated in this resin bath and the added plasticizer had goodhand, was'non-capillary and did not broom; Plasticizers' used' werealkyl aryl phosphates, phthalates, sebacates, citrates, epoxies and.polymeric dimethyl siloxanes;

The coating The polysiloxanes containing larger proportions of.

aryl groups require larger amountsof plasticizers. The

pick up can be readily varied by the pressure on the wipers. A slower.cure at a lower temperature gives a good coating. A more rapid cure isgenerally preferred, as the cure most conveniently takes place in atunnel, and if a slower cure is used the tunnel must be longer for agiven production rate and hence. is more expensive.

I claim:

1. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 6-0; picks per inch 40; denier ofraw silk used 112; and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being present inan amount at least sufficient to impart noncapillarity and not more than20% of the weight of the uncoated filaments.

2. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 5-0; picks per inch 40; denier ofraw silk used 252; and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being present inan amount at least sufiicient to impart noncapillarity and not more than20% of the weight of the uncoated filaments.

3. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, havingapproximately thefollowing construction: U.S.P. size 4-0; picks per inch 40; denier ofraw silk used 378; and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being present inan amount at least sufiicient to impart noncapillary and not more than20% of the weight of the uncoated filaments.

4. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 3-0; picks per inch 40; denier. of.raw silk used 630; and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being present inan amount at least sufiicient to impart noncapillarity and not more than20% of the weight of the uncoated filaments.

5. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 00; picks per inch 50; denier of rawsilk used 966; and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being present inan amount at least suificient to impart noncapillarity and not more than20% of the weight of the uncoated filaments.

6. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having ;a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 0; picks per inch 50; denier of rawsilk used 1560; and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being present inan amount at least sufiicient to impart noncapillarity and not more than20% of the Weight of the uncoated filaments.

7. The method of making surgical sutures comprising braiding a pluralityof filaments of silk into a hard dense core, washing the gum from thebraided silk, drying the braided silk, dry stretching the braided silkabout 6. to 11% of its length, immersing the braided silk in a xylenesolution of a polymerizable silicone, wiping the braided silk suture,whereby there is a silicone pick up of about to by weight, and dryingand polymerizing said silicone.

8. The method of making surgical Sutures comprising braiding a pluralityof filaments of silk into a hard dense core, washing the gum from thebraided silk, drying the braided silk, dry stretching the braided silkabout 6 to 11% of its length, immersing the braided silk in a solutionof a polymerizable silicone rubber containing a catalyst, wiping thebraided silk suture, whereby there is a silicone pick up of about 10% to20% by weight, and drying and polymerizing said silicone by heat, of atleast about 150 C. for at least about seconds, thereby also decomposingthe catalyst.

9. The method of making surgical sutures comprising braiding a pluralityof filaments of silk into a hard dense core, washing the gum from thebraided silk, drying the braided silk, dry stretching the braided silkabout 6 to 11% of its length, immersing the braided silk in nontoxicvolatile hydrocarbon solvent solution of a polymerizable silicone rubbercontaining a catalyst, wiping the braided silk suture, drying andpolymerizing said silicone, re-immersing in said solution, re-wiping thesuture, whereby there is a total silicone pick up of about 10% to 20% byweight, and drying and polymerizing said silicone by heat, of at leastabout 150 C. for at least about 30 seconds, thereby also decomposing thecatalyst.

10. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 6-0; picks per inch denier of rawsilk used 112; and a coating on each silk filament of a nontoxicphysiologically inert polymeric silicone, said coating Weighing from 10%to 20% of the weight of the silk filaments.

11. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 5-0; picks per inch 40; denier ofraw silk used 252; and a coating on each silk filament of a nontoxicphysiologically inert polymeric silicone, said coating weighing from 10%to 20% of the weight of the silk filaments.

12. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 4-0; picks per inch 40; denier ofraw silk used 378; and a coating on each silk filament of a nontoxicphysiologically inert polymeric silicone, said coating weighing from 10%to 20% of the weight of the silk filaments.

13. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 3-0; picks per inch 40; denier ofraw silk used 630; and a coating on each silk filament of a nontoxicphysiologically inert polymeric silicone, said coating weighing from 10%to 20% of the weight of the silk filaments.

14. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction: U.S.P. size 00; picks per inch denier of rawsilk used 966; and a coating on each silk filament of a nontoxicphysiologically inert polymeric silicone, said coating weighing from 10%to 20% of the weight of the silk filaments.

15. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, with high density, having approximately thefollowing construction:

10 U.S.P. size 0; picks per inch 50; denier of raw silk used 1560; and acoating on each silk filament of a non-toxic physiologically inertpolymeric silicone, said coating weighing from 10% to 20% of the weightof the silk filaments. V

16. A surgical suture comprising a plurality of individual filaments incoordinate configuration, the filaments being bonded together to holdthe filaments in a unitary strand, and hence non-brooming, having acoating on each filament of a non-toxic, physiologically inert,polymeric silicone, whereby the suture is non-capillary and is inerttowards livingtissue, the Weight of said silicone being from 10% to 20%of the weight of the uncoated filaments.

17. A surgical suture comprising a plurality of individual filamentsselected from the group consisting of silk, nylon, polypropylene andstretched oriented polyester, the external filaments being in braidedconfiguration, having a tight braid, and low pick count, with highdensity, thereby imparting surgically handleable char acteristics to theuncoated suture, and a coating on each filament of a non-toxicphysiologically inert polymeric silicone, whereby the suture isnon-capillary and is inert towards living tissue, the weight of saidsilicone being from 10% to 20% of the weight of the uncoated filaments.

18. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, and low pick count, with high density, therebyimparting surgically handleable characteristics to the uncoated suture,and a coating on each silk filament of a non-toxic physiologically inertpolymeric silicone, whereby the suture is noncapillary and is inerttowards living tissue, the weight of said silicone being from 10 %to 20%of the weight of the uncoated filaments.

19. A surgical suture comprising a plurality of individual silkfilaments in coordinate configuration, each filament having thereon acoating of a polymethyl-polyphenyl siloxane, at least the finalpolymerization being in situ, the weight of said silicone being from 10%to 20% of the Weight of the uncoated filaments, whereby the suture isnon-capillary and is inert towards living tissue, and the siloxanecoating causes the filaments to adhere to each other, and thereby befree from brooming, and which suture, when tied in a surgeons knot,breaks rather than slips, on pulling in tension.

20. The method of making surgical sutures comprising braiding aplurality of filaments of silk into a hard dense core, washing the gumfrom the braided silik, drying the braided silk, dry stretching thebraided silk about 6 to 11% of its length, immersing the braided silk ina xlyene solution of a polymeriza-ble silicone, wiping the braided silksuture, whereby there is a silicone pick up of an amount sufi'icient torender the finished suture non-capillary and not more than 20% of theweight of the uncoated -filaments,.and drying and polymerizing saidsilicone.

21. The method of making surgical sutures comprising braiding aplurality of filaments of silk into a hard dense core, washing the gumfrom the braided silk, drying the braided silk, dry stretching thebraided silk about 6 to 11% of its length, immersing the braided silk ina solution of a polymerizable silicone rubber containing a catalyst,wiping the braided silk suture, whereby there is a silicone pick up ofan amount sufiicient to render the finished suture non-capillary and notmore than 20% of the weight of the uncoated filaments, and drying andpolymerizing said silicone by heat, of at least about C. for at leastabout 30 seconds, thereby also decomposing the catalyst.

22. The method of making surgical sutures comprising braiding aplurality of filaments of silk into a hard dense core, washing the gumfrom the braided silk, drying the braided silk, dry stretching thebraided silk about 6 to 11% of its length, immersing the braided silk innon-toxic sues #52 l. volatile hydrocarbon solvent solution ofapolymerizable silicone rubber containing a catalyst, Wiping the braidedsilk suture, drying and polymerizing said silicone, reimmersing in saidsolution, re-wiping the suture, whereby there is a total silicone pickup of an amount sufficient silicone, said silicone being present in anamount at least sufiicient to impart non-capillarity and not more than20% of the Weight of the uncoated filaments, and the suture is inerttowards living tissue.

24. A surgical suture comprising a plurality of individual filamentsselected from the group consisting of silk,

nylon, polypropylene and stretched oriented polyester,

the external filaments being in braided configuration, having a tightbraid, and low pick count, with high density, thereby impartingsurgically handlea-ble characteristics to the uncoated suture, and acoating on each filament of a non-toxic physiologically inert polymericsilicone, said silicone being present in an amount at least sufiicientto impart non-capillarity and not more than 20% of the weight of theuncoat-e filaments, and the suture is inert towards living tissue.

25. A surgical suture comprising a plurality of individual silkfilaments, the external silk filaments being in braided configuration,having a tight braid, and low pick count, with high density, therebyimparting surgically handleable characteristics to the uncoatedsuture,.and a coating on each silk filament of a non-toxicphysiologically inert polymeric silicone, said silicone being presentin.

an amount at least suificient to impart non-capillarity and not morethan 20% of the weight of the uncoated filaments, and the suture isinert towards living tissue.

26. A surgical suture comprising a plurality of individual silkfilaments in coordinate configuration, each filament havingthereon acoating of a polymethyl-polyphenyl siloxane, at least the finalpolymerization being in situ, the weight of said silicone being anamount sufficient to render the finished suture non-capillary and notmore than 20% of the weight ofthe uncoated filaments, and said suture isinert towards living tissue, and the siloxane coating causes thefilaments to adhere to each other, and thereby be free from brooming,and which suture when when tied in a surgeons knot, breaks rather thanslips, on pulling in tention.

References Cited by the Examiner UNITED STATES PATENTS 2,193,188 3/40Bradley 128-6355 2,588,365 3/52 Dennett.

2,698,817 1/55 G'uenther 28--80 2,734,506 2/56 Nichols et al. l28-335.52,737,075 3/ 56 Poirier et al 872 3,035,476 5/62 Fogden 87-9 V FOREIGNPATENTS 876,208 8/61 Great Britain. 1,110,824 7/61 Germany.

RlCHARD A. GAUDET, Primary Examiner. JORDAN FRANKLIN, Examiner.

23. A SURGICAL SUTURE COMPRISING A PLUTALITY OF INDIVIDUAL FILAMENTS INCOORDINATE CONFIGURATION, THE FILAMENTS BEING BONDED TOGETHER TO HOLDTHE FILAMENTS IN A UNITARY STRAND, AND HENCE NON-BROOMING, HAVING ACOATING ON EACH FILAMENT OF A NON-TOXIC, PHYSIOLOGICAL INERT, POLYMERICSILICONE, SAID SILICONE BEING PRESENT IN AN AMOUNT AT LEAST SUFFICIENTTO IMPART NON-CAPILLARITY AND NOT MORE THAN 20% OF THE WEIGHT OF THEUNCOATED FILAMENTS, AND THE SUTURE IS INERT TOWARDS LIVING TISSUE.